BRPI0707114A2 - sdh (synchronous digital hierarchy) service transport and reception method via pon (passive optical network), sdh service method on pon, sdh service transmission and reception device, sdh gem frame data mapping method - Google Patents

Abstract

SDH SERVICE TRANSPORT AND RECEIVING METHOD SD SD (SD PID), PON OPTICAL NETWORK, PON SDH SERVICE METHOD The present invention relates to a method of transporting a synchronous digital hierarchy service in a passive optical network comprising: directly mapping a tax unit carrying the data of a synchronous digital hierarchy service to the GEM payload to perform SDH service data transport over a gigabit passive optical network. The encapsulation is removed by the opposite procedure at one receiving end. There is also a sending apparatus and a receiving apparatus for synchronous digital hierarchy service, and a method for mapping the synchronous digital hierarchy service data frame to a passive optical network data frame. It can be merged directly with the synchronous digital hierarchy network because the standard frame structure of the tax unit of a synchronous digital hierarchy is applied, and virtual container extraction comprising synchronous digital hierarchy service data, and service clock synchronization. are performed conveniently based on the tax unit's pointer adjustment mechanism.

Description

SDH SERVICE TRANSPORT AND RECEIVING METHOD BY SD METHOD DEVELOPMENT SERVICE BY PON (PASSIVE OPTICAL NETWORK), PON SDH SERVICE METHOD, TRANSMISSION AND RECEPTION DEVICE

FIELD OF INVENTION

The present invention relates to the field of communication technologies and, in particular, to a method and device for transmitting SDH services on a passive optical network.

BACKGROUND OF THE INVENTION

Passive Optical Network (PON) is a multipoint, one-point fiber optic access network that includes optical line terminals (OLT) at a central station end, optical network units (ONU), or optical network terminals (ONT) in the endpoint and an optical distribution network (ODN). With the development of PON technologies, Gigabit Optical Passive Networking (GPON) is becoming a hot spot for today's study. How to transport existing cost-effective SDH communication service across GPON networks in a cost-effective manner is an important problem that needs to be addressed in order for GPON to be promoted and supported by applications.

In SDH services, time division multiplexing services at various rates play an important role. Currently, in a GPON network, there are mainly two modes in which a TDM service is ported:

The first is "TDM over GEM" mode, in which the TDM service is mapped to a GEM (GPON Encapsulation Method) frame. According to this mode, TDM service is encapsulated using a fickle GEM frame length, and is transmitted to a limited extent between an OLT and an ONT; and because clock recovery is performed in an adaptive manner, it is difficult for clock recovery to meet the requirements of instability and variation control; and

The second is "TDM over Ethernet" mode, in which TDM service is transmitted via an Ethernet frame. Accordingly, an Ethernet quadrode-based code format is required and a higher transmission bandwidth is required and therefore the cost of a UN is increased.

To solve the above problems, an "SDH over GEM" mode is proposed, according to which SDH framework is used to implement TDM service conduction in a GPON network. Currently, there are mainly the two following methods of implementing "SDH over GEM".

The first method is to use a modified SDH virtual container (VC) to carry TDM service. Basically, the method includes: modifying SDH frame structures VCll is "VC12, mapping TDM services at rate T1 and rate E1 on modified frame structures of VCll and VC12 respectively, encapsulating each modified VCll and VC12 frame into a GEM frame, and transmitting TDM services According to this method, modification of the structure of a service frame for mapping is required, and an SDH frame cannot be transmitted to an ONT directly, a structured TDM service transmission cannot be performed because its structure is not standard; Byte tuning cannot be achieved because a virtual container provides only positive and reverse tuning and fill bits.

The second method is to encapsulate various TDM service types into frame structures of a virtualSDH tributary, in a data-frame skip payload form, or in a data structure locking payload form, or in a payload form. floating data structure indication using a pointer; and encapsulate the virtual tributary in an Ethernet frame, and encapsulate the Ethernet frame in the payload of a GEM frame, that is, TDM service is transported in GPON network in "Ethernet over GEM" mode. Although in this method it is not necessary to modify existing standards, the TDM service has to subtract to three mappings via VT, Ethernet and GPON. Thus, this method is complicated in its implementation, resulting in a high overall protocol cost and higher bandwidth.

SUMMARY OF THE INVENTION

The present invention provides a method and device for transporting and receiving SDH services in a passive optical network, which can be merged with an SDH network directly without modifying existing standard SDH tributary unit (TU) frame structure. Depending on the method and device, SDH service data can be extracted in a simplified manner.

The present invention also provides a method of mapping an SDH data frame into a passive optical network data frame, so that SDH service can be transmitted via a passive optical network.

The invention also provides a method of transporting an SDH service over a passive optical network (PON). 0 method includes:

encapsulating a tax unit by carrying SDH service data in a data frame of the encapsulation methodPON; and

pass the data frame of the encapsulation methodPON.

The present invention also provides a method of receiving an SDH service in a PON. The method includes:

receive a data frame from the encapsulation method PON; and

extract an SDH tax unit that is loaded into a payload portion of the PON encapsulation method data frame.

The present invention also provides a device for transmitting an SDH service. 0 device includes:

an encapsulation module adapted to encapsulate a tributary unit carrying SDH service data in a PON encapsulation method data frame; and

a transmission module adapted to transmit the data frame of the PON encapsulation method.

The present invention provides an SDH service receiving device. The device includes: a receiving module adapted to receive a quadrode data from the PON encapsulation method; and

a first de-encapsulation module adapted to extract from the PON encapsulation method data frame received by the receiving module, a tributary unit SDH which is loaded into a payload portion of the PON encapsulation method data frame.

The present invention also provides a method of mapping an SDH data frame to a PON data frame. 0 method includes:

map the entire data frame of an "SDH tax unit to a payload portion of the PON data frame; and

identify the type of tax unit in the payload portion of the PON data frame using a length indicator on a head of the PON data frame.

The present invention realizes SDHem GPON service transmission by adopting the method of directly mapping SDH tributary units into GEM frames. Because the standard SDH tributary unit quadrate structure is adopted in the present invention, the present invention can be merged with an SDH network and can implement simple conduction and extraction of SDH service data.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a schematic diagram of a method of transporting SDH service on a GP0N according to a first embodiment of the present invention.

Figure 2 is a schematic diagram of mapping a TU into a GEM frame according to the first embodiment of the present invention.

Figure 3 is a schematic diagram of loading TDM service data on TU paths according to the first embodiment of the present invention.

Figure 4 is a schematic diagram of structure TU-11 according to the first embodiment of the present invention.

Figure 5 is a schematic diagram of structure TU-12 according to the first embodiment of the present invention.

Figure 6 is a schematic diagram of structure TU-2 according to the first embodiment of the present invention.

Figure 7 is a schematic diagram of structure TU-3 according to the first embodiment of the present invention.

Figure 8 is a schematic diagram of an SDH service reception method in a GPON according to a second embodiment of the present invention.

Figure 9 is a schematic diagram of a method of receiving SDH services in a GPON according to a third embodiment of the present invention.

Figure 10 is a schematic diagram of the structure of an SDH service transmission device according to a fourth embodiment of the present invention.

Figure 11 is a schematic diagram of the structure of an SDH service receiving device according to a fifth embodiment of the present invention.

Figure 12 is a schematic diagram of the structure of an SDH service receiving device according to a sixth embodiment of the present invention.

DETAILED DESCRIPTION OF MODALITIES

One embodiment of the present invention provides a method for transporting and receiving SDH service in a passive optical network, whereby an SDH tributary unit carrying SDH service is directly mapped to GEM, thereby performing SDH service transmission in GPON. TDM services can be loaded at various rates into corresponding types of TUs according to the existing SDH specified encapsulation process. Different types of TUs are periodically loaded into GEM frames according to the same framing periods and are transmitted. At the receiving end, the de-encapsulation process is reverse engineered and SDH service data is routed or extracted. The receiving end may determine the type of a TU through the GEM Frame Payload Length Indicator (PLI), and may also negotiate the type of a GEM-transported TU through the UN eGovernment Control Interface (OMCI) .. In addition, for the purpose of preventing clock instability resulting from service downtime caused by situations such as a devariation process, according to one embodiment of the present. In this invention, several extracted tax units are stored embuffer at the receiving end that needs to forward services, and if there is a stop in receiving a frame due to the passive optical network encapsulation (PON) method the buffered tax units are used for transmission, therefore. preventing clock instability causes by a service stop. Embodiments of the present invention also provide the corresponding encapsulation and decapsulation devices. Methods and devices according to embodiments of the present invention will now be described in detail.

Modality 1: A method of transporting SDH service on a GPON is provided, as shown in Figure 1. The method includes the following steps:

101: Map a TU that carries SDH service on the payload of a GEM frame;

102: Add GEM frame header to form GEM frame;

103: Transmitting the GEM frame carrying the TU frame;

The process of encapsulating a TU carrying SDH service in a GEM frame is performed after steps 101 and 102 above.

In the embodiment, GEM frames of varying lengths are used to carry SDH TUs of various types. A TU is mapped to part of the payload of a GEM frame, and five cobobtes are added as a GEM header, and thus the GEM frame is formed, as shown in Figure 2. The head of a GEM frame includes the following four parts: Payload (PLI, 12bit), Port Identification (PID, 12bit), Payload Type Indicator (PTI, 3bit) and Header Error Control (HEC, 13bit). The length of the payload portion of a GEM frame that carries a TU is fixed and is determined by the structure of .TU.

TU can be obtained from SDH service data encapsulation, and can also be received from a device with an SDH interface. The process of encapsulating SDH service data as a TU will be briefly provided for describing TU structure and type.

TDM service, which is a type of SDH service, is taken as an example. Generally, TDM service data is of different types, such as TI, El, T2, T3, and T4, where T1 corresponds to a data rate of 1544 kbps, Elc corresponds to a data rate of 2048 kbps, T2 corresponds to a data rate of 6312 kbps, T3 corresponds to a data rate of 4 4736 kbps and E3 corresponds to a data rate of 34368 kbps.

In an SDH transmission structure, TUs are divided into three types: TU-1, TU-2 and TU-3, where TU-I further includes TU-Il and TU-22, which are used to carry El and TI respectively; TU-2 is used to carry T-2, and TU-3 is used to carry T-3 and E-3.

TDM service at these different data rates can be charged on different types of TUs according to the existing SDH specification on mapping and framing as shown in Figure 3. The unbundling process includes:

Step 1: Map TDM service data into corresponding SDH standard containers according to data rates of TDM service data;

Loading T1 and E1 into a standard container C-1, where T1 corresponds to a standard container C-II, and E1 corresponds to a standard container C-12; C-Il and C-12 are multiquads each including four subframes; C-Il has 4 (9 * 3-2) = 100bytes, and C-12 has 4 (9 * 4-2) = 136 bytes; the framing period for multi-frames C-11 and C-12 is 500 με;

Load T2 into a standard C-2 container; C-2 is a multi-frame including four subframes, C-2 has 4 (9x12-2) = 424 bytes, C-2 multi-frame framing period is 500 μs;

Load T3, E3 in a standard C-3 container; C-3 includes only one subframe and is 9x85 = 765 bytes, the C-3 multi-frame framing period is 125 με;

The default container primarily performs a mismatch function, such as rate adjustment. T DM service data, after being set to code rate in a standard container, is changed to a synchronous signal;

Step 2: Add Path Increment to standard C-n containers (n = 1,2,3) to form corresponding CV-n;

VC-1 POH (comprising VC-11 and VC-12) or VC-2 consists of four bytes: V5, J2, N2 and K4, which are added at the initial end of the four subframes to form VC-1/2 multiquads, respectively; V-5, which is the first byte of a multi-frame, provides functions such as error code detection, signal labeling, path status indication, etc .; J2 is a path trace byte, for low level channel access point indicator, N2 is a network operator byte, to provide a serial low level channel monitor function; the first to the fourth byte bit K4 are used for channel protection signaling, and the fifth to the seventh byte bit K4 are used to indicate distal end invalidation, and the eighth bit is reserved.

The VC-3 POH consists of nine bytes: J1, B3, C2, G1, F2, H4, F3, K3 and N1 and is classified in the first VC-3 frame structure column. J1 is a path trace byte for containing the high level path access point indicator; B3 contains BIP-8 channel code and has a function of monitoring high level channel error code; C2 is a signal label byte to indicate the multistructure and payload nature of a VC frame; Gl is a valid byte destatus of route to monitor status and performance of the route; F2 and F3 are bytes of path users to provide official business communication between path units; H4 is a position indicator byte for multi-frame payload and position payload indicators, the first to fourth byte bytes K3 are used to transmit channel protection signaling, and the fifth to eighth bytes are reserved; Nl is a byte network operator capable of providing serial monitoring function for high level paths.

Step 3: Add pointer overhead (bridgehead: PTR TU) to VC-n (n = 1,2,3) to form TU-n.

TU-1/2 / PTR includes four bytes: VI, V2, V3 and V4. V1 and V2 are real pointer bytes, to indicate position specified first byte V5 of multi-frame VC-1/2 on TU-1/2; V-3 is one byte of negative adjustment position; V4 is a reserved byte. The structures of TU-11, TU-12, and TU-2, which are formed by adding pointers to VC-n (n = 1,2,3), are shown in Figures 4, 5, and 6, respectively. Figure 4 shows the TU-11 block-like frame structure, where 4 rows χ (3> <9) columns are included. Similarly, Figure 5 shows the block-like frame structure of TU-12, where 4 rows χ (4> <9) columns are included and Figure 6 shows the block-like frame structure of TU-2, in which that 4 rows χ (12χ9) columns are included.

PTR TU-3 includes three bytes: H1, H2 and H3. H1 and H2 are bytes of practical pointers indicating amount of variation between the first byte J1 in frame VC-3 and the last byte H3 at the point; H3 is a negative adjustment position byte. TU-3, which is formed by adding pointers is shown in Figure 7. In Figure 7, the block-like frame structure of TU-3 is shown, where 9 rows χ 85 columns and 3 bytests included.

PTR TU pointers can be used to adjust payload bytes, to perform phase and frequency calibration, and to tolerate instability and frequency variation in the network. It can be obtained from the above TU framing period which, to ensure clock synchronization, TU -I eTU-2 are loaded into a frame. GEM once every 500 με are transmitted, and TU-3 is loaded into a GEM frame once every 125 με and are transmitted. Transmission periods are based on the GPON system clock, and therefore the GPON system clock is synchronized with the SDH transmission system clock, ensuring clock integrity.

The present invention accomplishes the SDHem GPON service transmission by adopting the method of directly mapping an SDH tributary unit in a GEM frame. As the standard SDH tributary unit quadrature structure is adopted in the present invention, the present invention can be merged with an SDH network and can implement SDH service data extraction that support VC and service clock synchronization based on the pointer adjustment mechanism adopted by the tax unit. .

In addition, one embodiment of the present invention also provides the specific solution of mapping TDM service to various data rates on different types of tax units and encapsulating them in GEM frames periodically, which may be applied to the existing GPON system.

Mode 2: A method of receiving SDH service in GPON is provided, the flow of which is shown in Figure 8. The method of mode 2 is a reverse process corresponding to that of mode 1, wherein the transmitted SDH service in mode 1 is received. The method includes:

801: Receive a GEM Frame.

802: Extract one TU in part of payload from GEM board; since the payload portion of the GEM frame carrying the TU is of fixed length; The type of transported TU can be determined through the GEM frame's PLI.

803: Perform TU transmission service as per its type or obtain corresponding SDH service data from TU payload.

If the device implementing the method of receiving this mode is -a central station equipment, for example, an OLT, TU service transmission may also be performed at step 803, for example, forwarding the TU to an SDH network which is connected and obviously , corresponding operations such as multiplexing, encapsulation, etc. may be performed as required during transmission. When TU service transmission is performed, the mechanism to prevent clock instability caused by stopping GEM frame reception is adopted, that is, several TUs are buffered, and when a stop occurs at GEM frame reception, the buffered TUs are buffered. are transmitted. A specific scenario of engine application is the process of reaching in a PON system. When the range procedure is performed on a PON system, all normal functioning UNO / ONT services will be interrupted by 2 frames, that is, if UN / ONT is in a transmit state, its transmission is halted by 2 frames. During these 2 frames, the OLT at the receiving end cannot receive a UN / OLT transmitted GEM frame, and the buffered TUs can be used for service transmission and therefore time instability caused by the service shutdown can be avoided.

If the device implementing the method of receiving this mode is a user-terminal terminal type equipment, eg OLT, etc., SDH service data acquisition can be performed at step 803. The acquisition process can be performed according to the standard SDH reception process, specifically including: specifying a VC in the TU based on a PTRTU pointer, extracting the VC, terminating the VC POH overhead, and getting SDH service data at the payload.

Mode 3: A method of receiving SDH service in GPON is provided, the flow of which is shown in Figure 9. The method of mode 3 is substantially the same as that of mode 2, and the difference is that in mode 3, the type of TU carried by GEM is negotiated through OMCI before data is received. The method includes the following steps:

901: Conduct a trade through OMCI, and get the GU-transported TU type indicator.

For example, an ONT in GPON initially reports to an OLT the type of TU to be transmitted by the ONT, the OLT prepares a response confirming that it has received the ONT report, it may also be that an OLT initially reports to an ONT of a TU type. to be transmitted by the OLT, ONT prepares a response confirming that it has received the OLT report. Of course, the mode of the present invention is not limited to the above negotiation mode, and other forms of negotiation may also be adopted.

902: Receive a GEM board.

903: Extract a TU that is loaded into the payload portion of the GEM board.

904: Transmit the TU according to its type or obtain corresponding SDH service data from the payload portion of the TU.

In this embodiment, SDH service is received and unencapsulated, considering features of the SDH service transmitted according to the Mode 1 method, unencapsulated TU service transmission is performed or the corresponding SDH service data is extracted from the TU payload. Furthermore, in this embodiment of the present invention, several extracted tax units are buffered on the receiving side which need to perform service routing. When there is a reception of PON encapsulation method data frames, buffered tributary units are transmitted, thereby avoiding relay instability during service shutdown caused by situations, such as the range process.

A system that is applied to the above transmission method will now be described in detail.

Mode 4: An SDH transmission device is provided, as shown in Figure 10. The method includes an encapsulation module 11 and a transmission module 12.

Encapsulation module 11 is used to encapsulate a tributary unit that carries SDH service data in a PON encapsulation method data frame. Encapsulation module 12 includes a mapping module 111 and a framing module 112.

Mapping module 111 is used to map a tax unit carrying SDH service data as part of a payload of a PON encapsulation method data frame.

Framing module 112 is used to add a PON encapsulation method data frame frame header to the PON encapsulation method data frame payload generated by mapping module 111 to form the PON encapsulation method data frame.

Transmission module 12 is used to transmit the PON encapsulation method data frame formed by the encapsulation module 11.

The SDH service transmission module of this mode can encapsulate and carry SDH service by adopting the method of Mode 1. The SDH service transmission module of this mode can be implemented flexibly in a practical network, for example it can be implemented in an OLT device at a station. can be deployed on a user-side UN or ONT device. SDH tax units can be directly mapped

GEM frames using the SDH service transmission device of this mode and thereby performing the SDH service transmission in GPON. The standard structure of the SDH tax unit can be adopted, and therefore the device of the present invention can be fused to the SDH network directly, and VC extraction that includes SDH service data and service clock synchronization can be conveniently achieved based on adjusting mechanism of the tax unit pointer.

In addition, the device of this mode also provides a specific solution of mapping different data rate TDM services on different types of tributary units and encapsulating the TUs in GEMperiodic frames so that the mode device can be applied to the existing GPON system.

Embodiment 5: An SDH service receiving device is provided as shown in Figure 11. The device includes a receiving module 21, a first decapsulation module 22 and a second decapsulation module23.

The receiving module 21 is used to receive a PON encapsulation method data frame.

The first decapsulation module 22 is used to extract tributary units that are loaded into the payload portion of the PON encapsulation method data frame.

The second decapsulation module 23 is used to obtain TDM service data from the payload portion of the tax units extracted by the first decapsulation module 22.

SDH service decapsulation devices of this mode can receive and decapsulate SDH services by adopting the Mode 2 method. The SDH service receiving device in a practical network can be employed on a UN / OLT device on the user side.

Embodiment 6: An SDH service receiving device is provided as shown in Figure 12. The method includes a receiving module 31, a first decapsulation module 32, a service transmission module 33 and a buffer module 34.

The receive module 31 is used to receive a PON encapsulation method data frame. The first unencapsulated module 32 is used to extract the SDH tax units in payload portion of the PON encapsulation method data frame received by the receive module 31.

The service transmission module 33 is used to transmit tax units extracted by the first decapsulated module 32.

Buffer module 34 is used to store embuffer several extracted tax units; and when a stop occurs on reception of the PON encapsulation method data frame, the embuffer stored tax units are provided to the service transmission module 33 for transmission.

The SDH service receiving device of this mode can receive and decapsulate SDH service by adopting the method of Modality 2. The SDH decapsulating device of this mode can be implemented in an LOL device at a central station such that a GPON network is directly connected to an SDH network for transmission. of the service.

SDH service reception devices of modalities 5 and 6 receive and de-encapsulate SDH service, considering the characteristics of SDH tax units being mapped in GEM frames to achieve SDH service transmission in GP0N; and perform service transmission of the obtained TUs or extract corresponding SDH service data from the GEM payload portion. In addition, the mode receiving device buffers tributary units on the receiving side that need to forward service, and when a stop occurs in the reception of PON encapsulation method finger frames, the buffered tributaries are transmitted, thereby avoiding resulting clock instability. stoppage of service caused by situations such as range.

The method and device for transporting and receiving TDM service provided by the embodiments of the present invention are explained in detail as above. While the present invention has been illustrated and described with reference to some preferred embodiments of the present invention, those skilled in the art will understand that various modifications may be made in form and detail, without departing from the spirit and scope of the present invention and, therefore, should fall within the scope of protection. of the present invention defined by the appended claims and their equivalents.

Claims (19)

1. Method of transporting SDH (synchronous digital hierarchy) service through passive optical network (PON), characterized by the fact that it comprises: encapsulating a tax unit carrying SDH service data in a GEM (GON Encapsulation Method) framework; and transmit the GEM frame. Transport method according to claim 1, characterized in that the encapsulation of a tax unit carrying SDH service data in a GEM frame comprises: mapping the tax unit into a payload portion of the GEM frame; a GEM frame header to form the GEM frame. Method of transport according to claim 2, characterized in that the tax unit comprises a first tax unit, a second tax unit and a third tax unit; Each tax unit is periodically mapped in the GEM chart according to its respective framing period and is transmitted. Transport method according to any one of claims 1 to 3, characterized in that the SDH service comprises a TDM service, and loading TDM service data into a tax unit comprises: mapping the TDM service data into a corresponding SDH standard container according to the data rate of the DM service data, adding path overhead to the standard container to form a virtual container; and add pointer overhead to form the tax unit. Transport method according to claim 3, characterized in that it further comprises: loading T1 service at a data rate of 1544 kbps and service El at a data rate of 204 8 kbps in the first tax unit; T2 at a data rate of 6312 kbps on the second tax unit; and load T3 service at a data rate of 44736 kbps and E3 service at a data rate of 34368 kbps on the third tax unit. Method of receiving SDH service via PON, characterized in that it comprises: receiving a GEM frame; and extracting an SDH tax unit that is loaded into a payload portion of the GEM board. Receipt method according to claim 6, characterized in that it further comprises: transmitting the SDH tax unit. Receiving method according to claim 7, characterized in that it further comprises: buffering multiple taxed units, and buffered tax units are transmitted when a frameGEM reception is stopped. Receipt method according to claim 6, characterized in that it further comprises: obtaining SDH service data from a tax unit payload. Receipt method according to claim 9, characterized in that obtaining SDH service data from a tax unit payload comprises: obtaining type of tax unit carried by the GEM framework; and extracting service data from a tax unit payload according to the type of tax unit. Receipt method according to claim 10, characterized in that obtaining the type of tax unit carried by the GEM table comprises: obtaining the type of tax unit carried by the GEM table according to a GEM table cargon length indicator ; or get type of tax unit carried by GEM framework through control interface negotiation. SDH service transmission device, characterized in that it comprises: an encapsulation module adapted to encapsulate a tributary unit carrying SDH service data in a GEM frame, a transmission module adapted to transmit the GEM frame generated from of the encapsulation module. Transmission device according to claim 12, characterized in that the encapsulation module comprises: a mapping module adapted to map the tributary unit in a payload portion of the GEM board; and a framing module adapted to add a GEM frame header to the payload portion of the GEM frame obtained from the mapping module to form the GEM frame. SDH service receiving device, characterized in that it comprises: a receiving module adapted to receive a GEM frame; and a first decapsulation module adapted to extract from the GEM board received by the receiving module an SDH tax unit which is loaded into a payload portion of the GEM board. Receiving device according to claim 14, characterized in that it further comprises: a second decapsulation module adapted to obtain TDM service data from the payload portion of the tax unit obtained from the first decapsulation module. Receiving device according to claim 14, characterized in that it further comprises: a service transmission module, adapted to transmit the SDH tax unit, and a buffer module, adapted to buffer several extracted tax units, and to provide the units buffered tributaries to the service transmission module for transmission when a stop occurs at reception of the GEM frame. 17. GEM framework SDH data frame mapping method, characterized in that it comprises: mapping the entire data frame of an SDH tax unit into a payload part of a GEM frame, and identifying type of tax unit in the payload part GEM frame using a length indicator in a GEM frame header. A mapping method according to claim 17, characterized in that the tax unit comprises: a first tax unit, a second tax unit, and a third tax unit. A mapping method according to claim 17, characterized in that when the tax unit is a first tax unit or a second tax unit, each tax unit is mapped to the payload portion of a GEM table; When the tax unit is a third tax unit, each tax unit is mapped to the useful part of a GEM table.